CO2 emission abatement in IGCC power plants by semiclosed cycles: Part A -With oxygen-blown combustion

This paper analyzes the fundamentals of IGCC power plants where cal bon dio xide produced by syngas combustion can be removed, liquefied and eventually disposed, to limit the environmental problems due to the "greenhouse effec t." To achieve this goal, a semiclosed-loop gas turbine cycle using an high ly-enriched CO2 mixture as working fluid was adopted. As the oxidizer, syng as combustion utilizes oxygen produced by an air separation unit. Combustio n gases mainly consist of CO2 and H2O: after expansion, heat recovery and w ater condensation a part of the exhausts, highly concentrated in CO2, can b e easily extracted compressed and liquefied for storage or disposal. A deta iled discussion about the configuration, and the thermodynamic performance of these plants is the aim of the paper. Proper attention was paid to: (i) the modelization of the gasification section and of its integration with th e power cycle, (ii) the optimization of the pressure ratio die the change o f the cycle working fluid (iii) the calculation of the power consumption of the "auxiliary" equipment, including the compression train of the separate d CO, and the air separation unit. The resulting over all efficiency is in the 38-39 percent range, with status-of-the-art gas turbine technology, but resorting to a substantially higher pressure ratio. The extent of modifica tions to the gas turbine engine, with respect to commercial units, was ther efore discussed. Relevant modifications are needed, brit not involving chan ges in the technology. A second plant scheme will be considered in the seco nd part of the paper, using air for syngas combustion and a physical absorp tion process to separate CO2 from nitrogen-rich exhausts. A comparison betw een the two options will be addressed there.